In a wireless communication device, a semiconductor integrated circuit that processes high-frequency received signals is used in many cases.
For example, in a semiconductor integrated circuit that forms a superheterodyne receiver for a radar, in addition to a filter capable of limiting the frequency band of received signals, there is a case that a polyphase filter or the like capable of suppressing image disturbing waves associated with frequency conversion of received signals is used.
The following Patent Literature 1 discloses a polyphase filter including a plurality of resistors and a plurality of capacitors.
The polyphase filter is originally used for generation of signals with a 90-degree phase difference, and the like, but is also capable of suppressing image disturbing waves.
In the polyphase filter, frequencies at which image disturbing waves can be suppressed change dependently on the resistance values of the resistors included therein and the capacitance values of the capacitors included therein.
A center frequency Fc of the frequencies at which image disturbing waves can be suppressed is represented by the following formula (1):
                              F          C                =                  1                      2            ⁢            π            ⁢                                                  ⁢            RC                                              (        1        )            
In formula (1), R represents the resistance values of the resistors and C represents the capacitance values of the capacitors.